This invention relates generally to surgical instruments for fastening bodily tissue. More specifically, it relates to instruments carrying an anvil upon which staples are formed to fasten the tissue.
Surgical staplers include a fastener assembly carrying an anvil upon which staples are fired. Linear staplers fire vertical rows of staples to fasten tissue. The fastener assembly includes not only the anvil but also a cartridge carrying the staples to be fired. Tissue is first clamped between the cartridge and anvil, and then the staples are fired from the cartridge, through the tissue and against the anvil where the staples are formed. Linear staplers come in different sizes, depending on the desired length of vertical rows of the staples which need to be placed to fasten the tissue. The cartridge has an elongated housing, and vertical rows of slots in the housing to receive the staples. Correspondingly, the anvil has an elongated body, and vertical rows of pockets on its tissue contacting surface. Each pocket is in alignment with a corresponding slot in the housing of the cartridge. When tissue is clamped between the elongated cartridge and housing, the staples are fired from the slots against the pockets on the anvil.
After a linear stapler is fired, it is frequently necessary to cut the fastened tissue on one side of the staple row with a scalpel. However, in order to cut, a surface must exist which allows the user to exert pressure against the surface while concurrently cutting tissue in a direction generally parallel to the staple row which has been fired into tissue. Frequently, the jaw providing the main frame subassembly for the fastener assembly, often referred to as the "hook", provides the cutting surface. This is so because the hook has a channel into which the anvil is placed. In other words, the anvil is sandwiched between the sidewalls of the channel. The tissue contacting surface of the anvil which contains the pockets against which the staples are formed extends beyond the channel, and the edge surfaces on the sidewalls of the channel can then provide the cutting surface for the scalpel when tissue needs to be cut after the staples are fired.
Unfortunately, the edge surfaces of the sidewalls of the channels on the "hook" do not provide a well-defined edge against which a scalpel can be placed for ease of curing stapled tissue. This edge does not provide a consistent margin between the staple line and the cut location.
Alternately, the construction of the linear stapler can be modified such that the hooks are sandwiched between the anvil. The tissue contacting surface of the anvil which contains the pockets against which the staples are formed extends beyond the hooks. Therefore, the edge surfaces forming the cutting guide on the sidewalls of the channel are covered by the anvil. In this configuration, the hook and anvil assembly are narrower. This narrower assembly permits better and easier access to the tissue which is to be stapled. Unfortunately, while better access with this particular configuration may be obtained, there is no cutting guide present in the instrument.
In view of the deficiencies inherent with surgical fastener assemblies of surgical staplers, what is needed is an anvil for the surgical fastener assembly which incorporates the feature of a uniform cutting guide to cut the stapled tissue. What is needed is a guide which will not change its relative location or size, unlike the conventional use of the edge of the sidewalls of the hooks in which the anvil is routinely placed. Ideally, this guide can be used with a narrow hook and anvil assembly. Furthermore, what is needed is a cutting guide for an anvil which provides a well-defined edge or surface against which a scalpel can be placed for ease of cutting stapled tissue. Finally, a cutting guide which can provide a consistent margin between the staple row and the cut location would be highly desirable.